This disclosure relates to color-stable thermoplastic compositions, and in particular to color-stable thermoplastic polymer compositions comprising polyaryl ester, methods of manufacture, and uses thereof.
Thermoplastic polymers of various compositions, such as polyesters and polyester-polycarbonate copolymers, are useful in the manufacture of articles and components for a wide range of applications such as automotive parts, electronic appliances, and numerous others. Because of their broad use, it is often necessary for various reasons, including aesthetic and functional reasons, to provide plastic articles and components according to targeted color specifications, which is often accomplished by incorporating dyes or pigments into the polymer melt. It can also be important that the color of the thermoplastic composition is stable after exposure to various conditions such as heat exposure, light exposure (including ultraviolet (UV) light exposure), etc. Many polymers, including the above-described polyesters and polyester-polycarbonate copolymers, have been found to be subject to yellowing after light exposure, which can adversely impact the color stability performance of a thermoplastic composition. This yellowing phenomenon, sometimes referred to as photoyellowing, is often addressed with various technologies such as UV absorbers (UVA's), stabilizers such as hindered amine light stabilizers (HALS), and dyes and pigments (e.g., for color compensation, light filtration, or combinations thereof).
Polyaryl esters, as the term is used herein, include polyesters derived from aromatic diacids (i.e., polyarylates) and from aromatic diols. Polyaryl esters are known to be susceptible to photoyellowing that has been difficult to address with known techniques and materials, especially for some colors and/or some shades of some colors. Accordingly, there remains a need for new solutions to addressing color stability of polyaryl esters across a variety of targeted color specifications.